C augmented scale.
The augmented scale, also known as the whole-tone scale, is a scale that divides the octave into six equal intervals of a whole tone each. There are no half-tone (semitone) intervals at all.
The augmented scale has a 'floating' sound characteristic, and establishes no specific key-center. In fact, because of its unique step-pattern, with the absence of semitones, it sounds the same whatever note you start from. Therefore, only two whole-tone scales are needed in order to cover all twelve keys. One starts from C and the other from C♯/D♭. The note you choose to play first gives the scale its name.
The augmented scale allows harmonic transitions not possible with conventional diatonic harmony, and as such is a very useful compositional device.